Preferential solute flow in intact soil columns measured by SPECT scanning

Single photon emission computed tomography (SPECT) is an imaging technique that is widely used in medical diagnosis. This technique has never been app lied to soils. The objective of this study was to investigate the capabilit ies of SPECT scanning for visualizing preferential flow in soil. This paper describes the principle of SPECT scanning and its application to tracer br eakthroughs in four large undisturbed soil columns (800-mm length x 77-mm d iam.). This new approach allows real-time analysis of flow patterns of radi oactive tracers in 2-D using planar imaging, and in 3-D using the tomograph ic capabilities of the SPECT scanner. Not only does SPECT scanning provide qualitative data, but it also allows for the quantification of a tracer's s patial distribution. Our results chararterized preferential now very clearl y in soil columns. SPECT scanning opens up ne,v avenues for 2-D and 3-D tra cer studies in porous media such as soils.